CHAPTER 4

CPAN Module 

Distributions

A CPAN 

MODULE IS

 released into an unpredictable environment. Nothing is certain 

operating system, version of Perl, and the availability of other modules will vary 

from user to user. To combat this variability, CPAN modules come packaged in 

module distributions. A module distribution includes all the files necessary to 

build, test, and install your module.

The portability of module distributions is at the core of what makes CPAN so 

extraordinarily successful. Many languages have repositories containing freely 

available code modules. But only Perl's has the capability to automatically install 

these modules on every supported platform with no appreciable work required on 

the user's part. This chapter will show you how your modules can be packaged to 

take full advantage of this remarkable capability.

Chapter 1 included examples of installing modules from module distributions; 

in this chapter, I'll briefly expand on how CPAN module installation works. Then 

I'll explain how to build them. Along the way, I'll also describe refinements in con 

structing the module itself for maximum portability.

Module Installation

Modules are installed from module distributions using a few simple steps. The 

CPAN module automates these steps, but let's look at how they work manually. I'll 

be demonstrating this process on a UNIX system (Redhat Linux to be precise), but 

with the proper tools listed in Chapter 1 installed, the examples should work on 

Windows too.

First, you download and uncompress the module. For example, I use

1

2

lwp download  to download the Memoize  module from CPAN:

$ lwp download http://www.cpan.org/authors/id/M/MJ/MJD/Memoize 1.00.tar.gz

Saving to  Memoize 1.00.tar.gz ...

46.2 KB received in 1 seconds (46.2 KB/sec)

1. lwp download is installed with the LWP module by Gisle Aas.

2. Written by Mark Jason Dominus

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